From: Nicholas Piggin <npiggin@gmail.com>
Date: Mon, 14 Sep 2020 14:52:17 +1000
Subject: powerpc: select ARCH_WANT_IRQS_OFF_ACTIVATE_MM
Git-commit: 66acd46080bd9e5ad2be4b0eb1d498d5145d058e
Patch-mainline: v5.10-rc1
References: MM Functionality, bsc#1178426

powerpc uses IPIs in some situations to switch a kernel thread away
from a lazy tlb mm, which is subject to the TLB flushing race
described in the changelog introducing ARCH_WANT_IRQS_OFF_ACTIVATE_MM.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200914045219.3736466-3-npiggin@gmail.com

Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
---
 arch/powerpc/Kconfig                   |    1 +
 arch/powerpc/include/asm/mmu_context.h |    2 +-
 2 files changed, 2 insertions(+), 1 deletion(-)

--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -152,6 +152,7 @@ config PPC
 	select ARCH_USE_QUEUED_RWLOCKS		if PPC_QUEUED_SPINLOCKS
 	select ARCH_USE_QUEUED_SPINLOCKS	if PPC_QUEUED_SPINLOCKS
 	select ARCH_WANT_IPC_PARSE_VERSION
+	select ARCH_WANT_IRQS_OFF_ACTIVATE_MM
 	select ARCH_WEAK_RELEASE_ACQUIRE
 	select BINFMT_ELF
 	select BUILDTIME_EXTABLE_SORT
--- a/arch/powerpc/include/asm/mmu_context.h
+++ b/arch/powerpc/include/asm/mmu_context.h
@@ -216,7 +216,7 @@ static inline void switch_mm(struct mm_s
  */
 static inline void activate_mm(struct mm_struct *prev, struct mm_struct *next)
 {
-	switch_mm(prev, next, current);
+	switch_mm_irqs_off(prev, next, current);
 }
 
 /* We don't currently use enter_lazy_tlb() for anything */